GEOLOGICAL SURVEY OF INDIA. 243 



and Gwadar consist of great horizontal plateaux surrounded by 

 cliffs of whitish marl or clay, and capped by dark calcareous grit. 

 These remarkable rocks have been called the Makran group, and 

 though the coast of Baluchistan has never been examined 

 geologically, there appears a considerable amount of probability 

 that the marine Makran group may represent the Manchhars and 

 Siwalikks on the edge of the Indo-Gaugetic plain. 



The completion of the " Manual of the Geology of India " was 

 the jDrincipal event in 1878. Though not the first general de- 

 scription of the Geology of India it differed from most previous 

 works in the extent of the area described and the amount of 

 information. Since the establishment of the survey in 1851, 

 data in the shape of detached papers and reports had been 

 accumulating rapidly, and these were not even confined to the 

 official channels of publications but had overflowed into the 

 journals of various scientific societies throughout the world. There 

 was thus an urgent need of a general view of the existing 

 knowledge, and Mr. Medlicott and Mr. Blanford's efforts supplied 

 the want. While the work itself is a joint production, each chapter 

 bears the initials of its actual author. The first two volumes deal 

 with the more strictly scientific side of Indian Geology, while a 

 third volume of over 600 pages from the pen of Mr. Valentine Ball 

 treats of the Economic Geology of the country, its Mineralogy being 

 described by Mr. F. R. Mallet in the fourth and last volume. A 

 map on the scale of 64 miles to the inch and geologically coloured 

 forms a valuable accompaniment to the work. 



During the same year Mr. Hacket examined a very large area at 

 the northern extremity of the Arvali range, and extending up to the 

 Jumna at Delhi. Though not abundant in mineral wealth the Arvali 

 region contains several extensive mines, now abandoned, from which 

 in bygone times large quantities of copper and lead ores have been 

 extracted, and a number of small pits or burrows where ores in small 

 quantities were found. None of these mines, however, were worked 

 deeper than a few feet below the water level on account of the 

 difficulty of raising the water. Marble is of frequent occurrence 

 among the Arvali rocks, and is extensively quarried in several 

 places, the principal place being Makrana. It is generally white, 

 but coloured marbles are occasionally met with, and black marble 

 in one spot. 



